2 cycles for a 32-bit to 64-bit extension? I don't think that makes sense: for instance, on x86-64, there's no cast necessary, just use the %rax register instea

2 cycles for a 32-bit to 64-bit extension? I don't think that makes sense: for instance, on x86-64, there's no cast necessary, just use the %rax register instead of the %eax one (plus, memory addressing works fine with 32 bit registers directly). I believe the same is true of AArch64 (64-bit ARM) with the 32-bit register W0 being the bottom half of the 64-bit register X0.